Velocity feedforward

Configuration

To activate velocity feedforward in P-AXIS-00223 velocity feedforward and the output of the velocity feedforward value as additional command value has to be set up.

vorsteuer.vorsteuerung 0x101 #0x001: Activation velocity feedforward
#0x100: Output as add. vel. command value

In the cyclic process date, the additive command value has to be configured.

Velocity feedforward 1:

If output of velocity feedforward as additive velocity command value is configured and no additive command velocity value is configured in the cyclic process data an error message 70350 (see P-ERR-70350) is output.

Velocity scaling

Now velocity scaling must be set up with the parameters P-AXIS-00205, P-AXIS-00206 and P-AXIS-00207.

In parameter P-AXIS-00205 the resulting velocity of the axis (under consideration of all transmission elements such as gearbox ratios and leadscrew pitch) must be entered when the value of P-AXIS-00206 is output on the velocity interface.

Example:

For a SERCOS-Drive with a leadscrew pitch of 10 mm/rev and default scaling of the velocity command values (10-4 U/min) an output of 10000 as velocity command value results in a translatory velocity of the axis of 10 mm/min ( (10000 * 10-4U/min * 10 mm/U). So the parameters P-AXIS-00205, P-AXIS-00206 and P-AXIS-00207 have to be set to the following values.

antr.v_time_base 0 #Timebase per Minute
antr.v_reso_num 10000 #Outputvalue to drive
antr.v_reso_denom 10000 #Resulting axis velocity in um/v_time_base

If an additional gearbox with a gearbox ratio of 3 (nmotor/nload) is considered, for the same output value the translatory axis velocity is reduced to 3,333 mm/min (10000 * 10-4U/min / i * 10 mm/U). This results in the following values for P-AXIS-00206 and P-AXIS-00207:

antr.v_time_base 0 #Timebase per Minute
antr.v_reso_num 10000 #Outputvalue to drive
antr.v_reso_denom 3333 #Resulting axis velocity in um/v_time_base

Additionally, the output of the velocity feedforward value can be delayed compared to the position command value. this delay can be set up with parameter P-AXIS-00389.

Velocity feedforward 2:

The maximum delay time that can be set up is one interpolator cycle. If a bigger delay time is set up an error message 70349 (see P-ERR-70349) is output and the delay time is set to zero.

The resulting parameter set is:

vorsteuer.vorsteuerung 0x101 #0x001: Activation velocity feedforward
#0x100: Output as add. vel. command value
vorsteuer.velocity_delay_time 150 # Delay velocity feedforward against
# position command value in us
antr.v_time_base 0 #Timebase per Minute
antr.v_reso_num 10000 #Outputvalue to drive
antr.v_reso_denom 3333 #Resulting axis velocity in um/v_time_base